Annotation of html5/workers/Overview.html, revision 1.93
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145: </style><link href=http://www.w3.org/StyleSheets/TR/%57%33%43-ED rel=stylesheet type=text/css><!-- ZZZ ED vs WD --><div class=head>
1.81 ihickson 146: <p><a href=http://www.w3.org/><img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72></a></p>
1.54 ihickson 147: <h1>Web Workers</h1>
1.92 ihickson 148: <h2 class="no-num no-toc" id=editor-s-draft-date-zzz-9-june-2008><!-- "W3C Working Draft" --> Editor's Draft <!--ZZZ-->24 March 2009</h2>
1.1 ihickson 149: <dl><!-- ZZZ: update the month/day
150: <dt>This Version:</dt>
1.77 ihickson 151: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090101/">http://www.w3.org/TR/2009/WD-workers-20090101/</a></dd>
1.2 ihickson 152: <dt>Latest Published Version:</dt>
153: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.81 ihickson 154: :ZZZ --><dt>Latest Editor's Draft:</dt>
155: <dd><a href=http://dev.w3.org/html5/workers/>http://dev.w3.org/html5/workers/</a></dd>
156: <!-- ZZZ: add the new version after it has shipped
1.2 ihickson 157: <dt>Previous Versions:</dt>
158: <dd><a href="http://www.w3.org/TR/2008/WD-workers-20080101/">http://www.w3.org/TR/2008/WD-workers-20080101/</a>
159: :ZZZ -->
1.81 ihickson 160: <dt>Editors:</dt>
161: <dd><a href=mailto:ian@hixie.ch>Ian Hickson</a>, Google, Inc.</dd>
162: </dl><p class=copyright><a href=http://www.w3.org/Consortium/Legal/ipr-notice#Copyright>Copyright</a>
163: © 2008 <a href=http://www.w3.org/><abbr title="World Wide
164: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href=http://www.csail.mit.edu/><abbr title="Massachusetts
165: Institute of Technology">MIT</abbr></a>, <a href=http://www.ercim.org/><abbr title="European Research
166: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href=http://www.keio.ac.jp/>Keio</a>), All Rights Reserved. W3C
167: <a href=http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer>liability</a>,
168: <a href=http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks>trademark</a>
169: and <a href=http://www.w3.org/Consortium/Legal/copyright-documents>document
170: use</a> rules apply.</p>
1.1 ihickson 171:
172: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.81 ihickson 173: <p class="alt copyright">The <a href=http://www.whatwg.org/specs/web-workers/current-work/>WHATWG
174: version</a> of this specification is available under a more
175: permissive license.</p>
1.1 ihickson 176: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
177:
1.81 ihickson 178: </div><hr><h2 class="no-num no-toc" id=abstract>Abstract</h2><p>This specification defines an API that allows Web application
179: authors to spawn background workers running scripts in parallel to
180: their main page. This allows for thread-like operation with
181: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id=status-of-this-document>Status of this document</h2><!-- intro boilerplate (required) --><p><em>This section describes the status of this document at the
182: time of its publication. Other documents may supersede this
183: document. A list of current W3C publications and the most recently
184: formally published revision of this technical report can be found in
185: the <a href=http://www.w3.org/TR/>W3C technical reports index</a>
186: at http://www.w3.org/TR/.</em></p><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.90 ihickson 187: them to <a href=mailto:public-webapps@w3.org>public-webapps@w3.org</a>
188: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
189: <a href=http://lists.w3.org/Archives/Public/public-webapps/>archives</a>)
1.81 ihickson 190:
191: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
192: or <a href=mailto:whatwg@whatwg.org>whatwg@whatwg.org</a> (<a href=http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org>subscribe</a>,
193: <a href=http://lists.whatwg.org/pipermail/whatwg-whatwg.org/>archives</a>).
1.1 ihickson 194: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
195:
1.81 ihickson 196: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
197: stable. <strong>Implementors who are not taking part in the
198: discussions are likely to find the specification changing out from
199: under them in incompatible ways.</strong> Vendors interested in
200: implementing this specification before it eventually reaches the
201: Candidate Recommendation stage should join the aforementioned
202: mailing lists and take part in the discussions.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) --><p>The latest stable version of the editor's draft of this
203: specification is always available on <a href=http://dev.w3.org/html5/workers/Overview.html>the W3C CVS
204: server</a> and in the <a href=http://svn.whatwg.org/webworkers/>WHATWG Subversion
205: repository</a>. The latest editor's working copy (which may contain
206: unfinished text in the process of being prepared) is available <a href=http://www.whatwg.org/specs/web-workers/current-work/>on the
207: WHATWG site</a>. Detailed change history can be obtained from the
208: following locations:</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><ul><li>Twitter messages (non-editorial changes only): <a href=http://twitter.com/WHATWG>http://twitter.com/WHATWG</a></li>
209: <li>Interactive Web interface: <a href=http://html5.org/tools/web-workers-tracker>http://html5.org/tools/web-workers-tracker</a></li>
210: <li>Commit-Watchers mailing list: <a href=http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org>http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></li>
211: <li>Subversion interface: <a href=http://svn.whatwg.org/webworkers/>http://svn.whatwg.org/webworkers/</a></li>
212: <li>CVS log: <a href=http://dev.w3.org/cvsweb/html5/workers/Overview.html>http://dev.w3.org/cvsweb/html5/workers/Overview.html</a></li>
213: </ul><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) --><p>The W3C <a href=http://www.w3.org/2008/webapps/>Web Apps
214: Working Group</a> is the W3C working group responsible for this
215: specification's progress along the W3C Recommendation track.
216: <!--ZZZ:-->
1.92 ihickson 217: This specification is the 24 March 2009 <!--ZZZ "Working Draft"-->Editor's Draft.
1.81 ihickson 218: <!--:ZZZ-->
219: </p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- relationship to other work (required) --><p>This specification is also being produced by the <a href=http://www.whatwg.org/>WHATWG</a>. The two specifications are
220: identical from the table of contents onwards.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) --><p>This specification is intended to specify a part of the Web
221: platform closely related to HTML5. It is defined in a separate
222: document primarily to ease the cognitive load on reviewers.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate --><p>This document was produced by a group operating under the <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/>5
223: February 2004 W3C Patent Policy</a>. W3C maintains a <a href=http://www.w3.org/2004/01/pp-impl/42538/status rel=disclosure>public list of
224: any patent disclosures</a> made in connection with the deliverables
225: of the group; that page also includes instructions for disclosing a
226: patent. An individual who has actual knowledge of a patent which the
227: individual believes contains <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential>Essential
228: Claim(s)</a> must disclose the information in accordance with <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure>section
229: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id=contents>Table of contents</h2>
230: <!--begin-toc-->
231: <ol class=toc>
232: <li><a href=#introduction><span class=secno>1 </span>Introduction</a>
233: <ol>
234: <li><a href=#scope><span class=secno>1.1 </span>Scope</a></li>
235: <li><a href=#tutorial><span class=secno>1.2 </span>Tutorial</a>
236: <ol>
237: <li><a href=#a-background-number-crunching-worker><span class=secno>1.2.1 </span>A background number-crunching worker</a></li>
238: <li><a href=#a-worker-for-updating-a-client-side-database><span class=secno>1.2.2 </span>A worker for updating a client-side database</a></li>
239: <li><a href=#worker-used-for-background-i-o><span class=secno>1.2.3 </span>Worker used for background I/O</a></li>
240: <li><a href=#shared-workers><span class=secno>1.2.4 </span>Shared workers</a></li>
241: <li><a href=#delegation><span class=secno>1.2.5 </span>Delegation</a></li>
1.82 ihickson 242: <li><a href=#providing-libraries><span class=secno>1.2.6 </span>Providing libraries</a></ol></ol></li>
243: <li><a href=#conformance-requirements><span class=secno>2 </span>Conformance requirements</a>
244: <ol>
245: <li><a href=#dependencies><span class=secno>2.1 </span>Dependencies</a></ol></li>
246: <li><a href=#terminology><span class=secno>3 </span>Terminology</a></li>
247: <li><a href=#infrastructure><span class=secno>4 </span>Infrastructure</a>
1.81 ihickson 248: <ol>
1.82 ihickson 249: <li><a href=#the-global-scope><span class=secno>4.1 </span>The global scope</a>
1.81 ihickson 250: <ol>
1.82 ihickson 251: <li><a href=#the-workerglobalscope-abstract-interface><span class=secno>4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
252: <li><a href=#dedicated-workers-and-the-dedicatedworkerglobalscope-interface><span class=secno>4.1.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
253: <li><a href=#shared-workers-and-the-sharedworkerglobalscope-inteface><span class=secno>4.1.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> inteface</a></ol></li>
254: <li><a href=#base-urls-and-origins-of-workers><span class=secno>4.2 </span>Base URLs and origins of workers</a></li>
1.85 ihickson 255: <li><a href=#decoding-scripts><span class=secno>4.3 </span>Decoding scripts</a></li>
256: <li><a href=#the-event-loop><span class=secno>4.4 </span>The event loop</a></li>
257: <li><a href=#the-worker-s-ports><span class=secno>4.5 </span>The worker's ports</a></li>
258: <li><a href=#processing-model><span class=secno>4.6 </span>Processing model</a>
1.81 ihickson 259: <ol>
1.85 ihickson 260: <li><a href=#runtime-script-errors><span class=secno>4.6.1 </span>Runtime script errors</a></ol></li>
261: <li><a href=#creating-workers><span class=secno>4.7 </span>Creating workers</a>
1.81 ihickson 262: <ol>
1.85 ihickson 263: <li><a href=#the-abstractworker-abstract-interface><span class=secno>4.7.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
264: <li><a href=#dedicated-workers-and-the-worker-interface><span class=secno>4.7.2 </span>Dedicated workers and the <code>Worker</code> interface</a></li>
265: <li><a href=#shared-workers-and-the-sharedworker-interface><span class=secno>4.7.3 </span>Shared workers and the <code>SharedWorker</code> interface</a></ol></ol></li>
1.82 ihickson 266: <li><a href=#apis-available-to-workers><span class=secno>5 </span>APIs available to workers</a>
1.81 ihickson 267: <ol>
1.82 ihickson 268: <li><a href=#importing-scripts-and-libraries><span class=secno>5.1 </span>Importing scripts and libraries</a></li>
1.93 ! ihickson 269: <li><a href=#the-navigator-object><span class=secno>5.2 </span>The <code title=worker-Navigator>Navigator</code> object</a></li>
1.82 ihickson 270: <li><a href=#apis-defined-in-other-specifications><span class=secno>5.3 </span>APIs defined in other specifications</a></li>
271: <li><a href=#interface-objects-and-constructors><span class=secno>5.4 </span>Interface objects and constructors</a></li>
272: <li><a href=#worker-locations><span class=secno>5.5 </span>Worker locations</a></ol></li>
1.81 ihickson 273: <li><a class=no-num href=#references>References</a></li>
274: <li><a class=no-num href=#acknowledgements>Acknowledgements</a></ol>
275: <!--end-toc--><hr><h2 id=introduction><span class=secno>1 </span>Introduction</h2><h3 id=scope><span class=secno>1.1 </span>Scope</h3><p><em>This section is non-normative.</em><p>This specification defines an API for running scripts in the
276: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
277: scripts that respond to clicks or other user interactions, and
278: allows long tasks to be executed without yielding to keep the page
279: responsive.<p>Workers (as these background scripts are called herein) are
280: relatively heavy-weight, and are not intended to be used in large
281: numbers. For example, it would be inappropriate to launch one worker
282: for each pixel of a four megapixel image. The examples below show
283: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
284: start-up performance cost, and a high per-instance memory cost.<h3 id=tutorial><span class=secno>1.2 </span>Tutorial</h3><p><em>This section is non-normative.</em><p>There are a variety of uses that workers can be put to. The
285: following subsections show various examples of this use.<h4 id=a-background-number-crunching-worker><span class=secno>1.2.1 </span>A background number-crunching worker</h4><p><em>This section is non-normative.</em><p>The simplest use of workers is for performing a computationally
286: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
287: (naïvely) compute prime numbers, and progressively displays the
288: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
289: <html>
290: <head>
291: <title>Worker example: One-core computation</title>
292: </head>
293: <body>
294: <p>The highest prime number discovered so far is: <output id="result"></output></p>
295: <script>
1.50 ihickson 296: var worker = new Worker('worker.js');
297: worker.onmessage = function (event) {
1.54 ihickson 298: document.getElementById('result').textContent = event.data;
1.29 ihickson 299: };
1.81 ihickson 300: </script>
301: </body>
302: </html></pre><p>The <code title=dom-Worker><a href=#dom-worker>Worker()</a></code> constructor call
303: creates a worker and returns a <code><a href=#worker>Worker</a></code> object
304: representing that worker, which is used to communicate with the
305: worker. That object's <code title=handler-Worker-onmessage><a href=#handler-worker-onmessage>onmessage</a></code> event handler
306: attribute allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 307: search: while (true) {
308: n += 1;
309: for (var i = 2; i <= Math.sqrt(n); i += 1)
310: if (n % i == 0)
311: continue search;
312: // found a prime!
1.50 ihickson 313: postMessage(n);
1.81 ihickson 314: }</pre><p>The bulk of this code is simply an unoptimised search for a prime
315: number. To send a message back to the page, the <code title=dom-DedicatedWorkerGlobalScope-postMessage><a href=#dom-dedicatedworkerglobalscope-postmessage>postMessage()</a></code>
316: method is used to post a message when a prime is found.<p><a href=http://www.whatwg.org/demos/workers/primes/page.html>View this example online</a>.<h4 id=a-worker-for-updating-a-client-side-database><span class=secno>1.2.2 </span>A worker for updating a client-side database</h4><p><em>This section is non-normative.</em><p>In this example, the main document spawns a worker whose only
317: task is to listen for notifications from the server, and, when
318: appropriate, either add or remove data from the client-side
319: database.<p>Since no communication occurs between the worker and the main
320: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 321: new Worker('worker.js');
1.81 ihickson 322: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 323: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 324: server.onmessage = function (event) {
325: // data is in the format "command key value"
1.54 ihickson 326: var data = event.data.split(' ');
1.31 ihickson 327: switch (data[0]) {
328: case '+':
329: database.transaction(function(tx) {
330: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
331: });
332: case '-':
333: database.transaction(function(tx) {
334: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
335: });
336: }
1.81 ihickson 337: };</pre><p>This connects to the server using the <code>WebSocket</code>
338: mechanism and opens the local database (which, we presume, has been
339: created earlier). The worker then just listens for messages from the
340: server and acts on them as appropriate, forever (or until the main
341: page is closed).<p><a href=http://www.whatwg.org/demos/workers/database-updater/page.html>View
342: this example online</a>. (This example will not actually function,
343: since the server does not actually exist and the database is not
344: created by this sample code.)<h4 id=worker-used-for-background-i-o><span class=secno>1.2.3 </span>Worker used for background I/O</h4><p><em>This section is non-normative.</em><p>In this example, the main document uses two workers, one for
345: fetching stock updates for at regular intervals, and one for
346: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
347: <html>
348: <head>
349: <title>Worker example: Stock ticker</title>
350: <script>
1.33 ihickson 351: // TICKER
352: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 353: var ticker = new Worker('ticker.js');
1.33 ihickson 354:
355: // SEARCHER
1.50 ihickson 356: var searcher = new Worker('searcher.js');
1.33 ihickson 357: function search(query) {
1.50 ihickson 358: searcher.postMessage(query);
1.33 ihickson 359: }
360:
361: // SYMBOL SELECTION UI
362: function select(newSymbol) {
363: symbol = newSymbol;
1.50 ihickson 364: ticker.postMessage(symbol);
1.33 ihickson 365: }
1.81 ihickson 366: </script>
367: </head>
368: <body>
369: <p><output id="symbol"></output> <output id="value"></output></p>
370: <script>
1.50 ihickson 371: ticker.onmessage = function (event) {
1.54 ihickson 372: var data = event.data.split(' ');
1.33 ihickson 373: document.getElementById('symbol').textContent = data[0];
374: document.getElementById('value').textContent = data[1];
375: };
1.50 ihickson 376: ticker.postMessage(symbol);
1.81 ihickson 377: </script>
378: <p><label>Search: <input type="text" oninput="search(this.value)"></label></p>
379: <ul id="results"></ul>
380: <script>
1.50 ihickson 381: searcher.onmessage = function (event) {
1.54 ihickson 382: var data = event.data.split(' ');
1.33 ihickson 383: var results = document.getElementById('results');
384: while (results.hasChildNodes()) // clear previous results
385: results.removeChild(results.firstChild);
386: for (var i = 0; i < data.length; i += 1) {
387: // add a list item with a button for each result
388: var li = document.createElement('li');
389: var button = document.createElement('button');
390: button.value = data[i];
391: button.type = 'button';
392: button.onclick = function () { select(this.value); };
393: button.textContent = data[i];
394: li.appendChild(button);
395: results.appendChild(li);
396: }
397: };
1.81 ihickson 398: </script>
399: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
400: </body>
401: </html></pre><p>The two workers use a common library for performing the actual
402: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 403: try {
404: var xhr = new XMLHttpRequest();
405: xhr.open('GET', url, false);
406: xhr.send();
407: return xhr.responseText;
408: } catch (e) {
409: return ''; // turn all errors into empty results
410: }
1.81 ihickson 411: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 412: var timer;
413: var symbol;
414: function update() {
1.50 ihickson 415: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 416: timer = setTimeout(update, 10000);
417: }
1.50 ihickson 418: onmessage = function (event) {
1.33 ihickson 419: if (timer)
420: clearTimeout(timer);
1.54 ihickson 421: symbol = event.data;
1.33 ihickson 422: update();
1.81 ihickson 423: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 424: onmessage = function (event) {
1.54 ihickson 425: postMessage(get('search.cgi?' + event.data));
1.81 ihickson 426: };</pre><p><a href=http://www.whatwg.org/demos/workers/stocks/page.html>View this example online</a>.<h4 id=shared-workers><span class=secno>1.2.4 </span>Shared workers</h4><p><em>This section is non-normative.</em><p>In this example, multiple windows (viewers) can be opened that
427: are all viewing the same map. All the windows share the same map
428: information, with a single worker coordinating all the viewers. Each
429: viewer can move around independently, but if they set any data on
430: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
431: the viewers:<pre><!DOCTYPE HTML>
432: <html>
433: <head>
434: <title>Workers example: Multiviewer</title>
435: <script>
1.36 ihickson 436: function openViewer() {
437: window.open('viewer.html');
438: }
1.81 ihickson 439: </script>
440: </head>
441: <body>
442: <p><button type=button onclick="openViewer()">Open a new
443: viewer</button></p>
444: <p>Each viewer opens in a new window. You can have as many viewers
445: as you like, they all view the same data.</p>
446: </body>
447: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
448: <html>
449: <head>
450: <title>Workers example: Multiviewer viewer</title>
451: <script>
1.50 ihickson 452: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 453:
454: // CONFIGURATION
455: function configure(event) {
1.54 ihickson 456: if (event.data.substr(0, 4) != 'cfg ') return;
457: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 458: // update display to mention our name is name
459: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
460: // no longer need this listener
1.43 ihickson 461: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 462: }
1.53 ihickson 463: worker.port.addEventListener('message', configure, false);
1.36 ihickson 464:
465: // MAP
466: function paintMap(event) {
1.54 ihickson 467: if (event.data.substr(0, 4) != 'map ') return;
468: var data = event.data.substr(4).split(',');
1.36 ihickson 469: // display tiles data[0] .. data[8]
470: var canvas = document.getElementById('map');
471: var context = canvas.getContext('2d');
472: for (var y = 0; y < 3; y += 1) {
473: for (var x = 0; x < 3; x += 1) {
474: var tile = data[y * 3 + x];
475: if (tile == '0')
476: context.fillStyle = 'green';
477: else
478: context.fillStyle = 'maroon';
479: fillRect(x * 50, y * 50, 50, 50);
480: }
481: }
482: }
1.53 ihickson 483: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 484:
485: // PUBLIC CHAT
486: function updatePublicChat(event) {
1.54 ihickson 487: if (event.data.substr(0, 4) != 'txt ') return;
488: var name = event.data.substr(4).split(' ', 1);
489: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 490: // display "<name> message" in public chat
1.36 ihickson 491: var dialog = document.getElementById('public');
492: var dt = document.createElement('dt');
493: dt.textContent = name;
494: dialog.appendChild(dt);
495: var dd = document.createElement('dd');
496: dd.textContent = message;
497: dialog.appendChild(dd);
498: }
1.53 ihickson 499: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 500:
501: // PRIVATE CHAT
502: function startPrivateChat(event) {
1.54 ihickson 503: if (event.data.substr(0, 4) != 'msg ') return;
504: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 505: var port = event.ports[0];
1.36 ihickson 506: // display a private chat UI
507: var ul = document.getElementById('private');
508: var li = document.createElement('li');
509: var h3 = document.createElement('h3');
510: h3.textContent = 'Private chat with ' + name;
511: li.appendChild(h3);
512: var dialog = document.createElement('dialog');
513: var addMessage = function(name, message) {
514: var dt = document.createElement('dt');
515: dt.textContent = name;
516: dialog.appendChild(dt);
517: var dd = document.createElement('dd');
518: dd.textContent = message;
519: dialog.appendChild(dd);
520: };
521: port.onmessage = function (event) {
1.54 ihickson 522: addMessage(name, event.data);
1.36 ihickson 523: };
524: li.appendChild(dialog);
525: var form = document.createElement('form');
526: var p = document.createElement('p');
527: var input = document.createElement('input');
528: input.size = 50;
529: p.appendChild(input);
530: p.appendChild(document.createTextNode(' '));
531: var button = document.createElement('button');
532: button.textContent = 'Post';
533: p.appendChild(button);
534: form.onsubmit = function () {
535: port.postMessage(input.value);
536: addMessage('me', input.value);
537: input.value = '';
538: return false;
539: };
540: form.appendChild(p);
541: li.appendChild(form);
542: }
1.53 ihickson 543: worker.port.addEventListener('message', startPrivateChat, false);
1.81 ihickson 544: </script>
545: </head>
546: <body>
547: <h1>Viewer</h1>
548: <h2>Map</h2>
549: <p><canvas id="map" height=150 width=150></canvas></p>
550: <p>
551: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
552: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
553: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
554: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
555: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
556: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
557: </p>
558: <h2>Public Chat</h2>
559: <dialog id="public"></dialog>
560: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
561: <p>
562: <input type="text" name="message" size="50">
563: <button>Post</button>
564: </p>
565: </form>
566: <h2>Private Chat</h2>
567: <ul id="private"></ul>
568: </body>
569: </html>
570: </pre><p>There are several key things worth noting about the way the
571: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
572: processing function, the code here attaches multiple event
573: listeners, each one performing a quick check to see if it is
574: relevant for the message. In this example it doesn't make much
575: difference, but if multiple authors wanted to collaborate using a
576: single port to communicate with a worker, it would allow for
577: independent code instead of changes having to all be made to a
578: single event handling function.<p>Registering event listeners in this way also allows you to
579: unregister specific listeners when you are done with them, as is
580: done with the <code title="">configure()</code> method in this
581: example.<p>Finally, the worker:<pre>
1.36 ihickson 582: var nextName = 0;
583: function getNextName() {
584: // this could use more friendly names
585: // but for now just return a number
586: return nextName++;
587: }
588:
589: var map = [
590: [0, 0, 0, 0, 0, 0, 0],
591: [1, 1, 0, 1, 0, 1, 1],
592: [0, 1, 0, 1, 0, 0, 0],
593: [0, 1, 0, 1, 0, 1, 1],
594: [0, 0, 0, 1, 0, 0, 0],
595: [1, 0, 0, 1, 1, 1, 1],
596: [1, 1, 0, 1, 1, 0, 1],
597: ];
598:
599: function wrapX(x) {
600: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 601: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 602: return x;
603: }
604:
605: function wrapY(y) {
606: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 607: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 608: return y;
609: }
610:
1.50 ihickson 611: function sendMapData(callback) {
1.36 ihickson 612: var data = '';
613: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
614: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
615: if (data != '')
616: data += ',';
617: data += map[y][x];
618: }
619: }
1.50 ihickson 620: callback('map ' + data);
1.36 ihickson 621: }
622:
623: var viewers = {};
624: onconnect = function (event) {
1.84 ihickson 625: event.ports[0]._name = getNextName();
626: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
627: viewers[event.ports[0]._name] = event.port._data;
628: event.ports[0].postMessage('cfg ' + name);
629: event.ports[0].onmessage = getMessage;
630: sendMapData(event.ports[0].postMessage);
1.36 ihickson 631: };
632:
633: function getMessage(event) {
1.54 ihickson 634: switch (event.data.substr(0, 4)) {
1.36 ihickson 635: case 'mov ':
1.54 ihickson 636: var direction = event.data.substr(4);
1.36 ihickson 637: var dx = 0;
638: var dy = 0;
639: switch (direction) {
640: case 'up': dy = -1; break;
641: case 'down': dy = 1; break;
642: case 'left': dx = -1; break;
643: case 'right': dx = 1; break;
644: }
645: event.target._data.x = wrapX(event.target._data.x + dx);
646: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 647: sendMapData(event.target.postMessage);
1.36 ihickson 648: break;
649: case 'set ':
1.54 ihickson 650: var value = event.data.substr(4);
1.36 ihickson 651: map[event.target._data.y][event.target._data.x] = value;
652: for (var viewer in viewers)
1.50 ihickson 653: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 654: break;
655: case 'txt ':
656: var name = event.target._name;
1.54 ihickson 657: var message = event.data.substr(4);
1.36 ihickson 658: for (var viewer in viewers)
659: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
660: break;
661: case 'msg ':
662: var party1 = event._data;
1.54 ihickson 663: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 664: if (party2) {
665: var channel = new MessageChannel();
1.84 ihickson 666: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
667: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 668: }
669: break;
670: }
1.81 ihickson 671: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
672: the <code title=handler-SharedWorkerGlobalScope-onconnect><a href=#handler-sharedworkerglobalscope-onconnect>onconnect</a></code>
673: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
674: "msg" message from one viewer naming another viewer, it sets up a
675: direct connection between the two, so that the two viewers can
676: communicate directly without the worker having to proxy all the
677: messages.<p><a href=http://www.whatwg.org/demos/workers/multiviewer/page.html>View this example online</a>.<h4 id=delegation><span class=secno>1.2.5 </span>Delegation</h4><p><em>This section is non-normative.</em><p>With multicore CPUs becoming prevalent, one way to obtain better
678: performance is to split computationally expensive tasks amongst
679: multiple workers. In this example, a computationally expensive task
680: that is to be performed for every number from 1 to 10,000,000 is
681: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
682: <html>
683: <head>
684: <title>Worker example: One-core computation</title>
685: </head>
686: <body>
687: <p>The highest prime number discovered so far is: <output id="result"></output></p>
688: <script>
1.50 ihickson 689: var worker = new Worker('worker.js');
690: worker.onmessage = function (event) {
1.54 ihickson 691: document.getElementById('result').textContent = event.data;
1.40 ihickson 692: };
1.81 ihickson 693: </script>
694: </body>
695: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 696: var num_workers = 10;
697: var items_per_worker = 1000000;
698:
699: // start the workers
700: var result = 0;
701: var pending_workers = num_workers;
702: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 703: var worker = new Worker('core.js');
704: worker.postMessage(i * items_per_worker);
705: worker.postMessage((i+1) * items_per_worker);
706: worker.onmessage = storeResult;
1.40 ihickson 707: }
708:
709: // handle the results
710: function storeResult(event) {
1.54 ihickson 711: result += 1*event.data;
1.40 ihickson 712: pending_workers -= 1;
713: if (pending_workers <= 0)
1.50 ihickson 714: postMessage(result); // finished!
1.81 ihickson 715: }</pre><p>It consists of a loop to start the subworkers, and then a handler
716: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 717: onmessage = getStart;
1.40 ihickson 718: function getStart(event) {
1.54 ihickson 719: start = 1*event.data;
1.40 ihickson 720: onmessage = getEnd;
721: }
722:
723: var end;
724: function getEnd(event) {
1.54 ihickson 725: end = 1*event.data;
1.40 ihickson 726: onmessage = null;
1.66 ihickson 727: work();
1.40 ihickson 728: }
729:
1.66 ihickson 730: function work() {
1.40 ihickson 731: var result = 0;
732: for (var i = start; i < end; i += 1) {
733: // perform some complex calculation here
734: result += 1;
735: }
1.50 ihickson 736: postMessage(result);
737: close();
1.81 ihickson 738: }</pre><p>They receive two numbers in two events, perform the computation
739: for the range of numbers thus specified, and then report the result
740: back to the parent.<p><a href=http://www.whatwg.org/demos/workers/multicore/page.html>View this example online</a>.<h4 id=providing-libraries><span class=secno>1.2.6 </span>Providing libraries</h4><p><em>This section is non-normative.</em><p>Suppose that a cryptography library is made available that
741: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
742:
743: <dd>Takes a port, on which it will send two messages, first the
744: public key and then the private key.</dd>
745:
746: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
747:
748: <dd>Takes a port, to which any number of messages can be sent, the
749: first giving the public key, and the remainder giving the
750: plaintext, each of which is encrypted and then sent on that same
751: channel as the cyphertext. The user can close the port when it is
752: done encrypting content.</dd>
753:
754: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
755:
756: <dd>Takes a port, to which any number of messages can be sent, the
757: first giving the private key, and the remainder giving the
758: cyphertext, each of which is decrypted and then sent on that same
759: channel as the plaintext. The user can close the port when it is
760: done decrypting content.</dd>
1.49 ihickson 761:
1.81 ihickson 762: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 763: if (e.data == "genkeys")
1.84 ihickson 764: genkeys(e.ports[0]);
1.54 ihickson 765: else if (e.data == "encrypt")
1.84 ihickson 766: encrypt(e.ports[0]);
1.54 ihickson 767: else if (e.data == "decrypt")
1.84 ihickson 768: decrypt(e.ports[0]);
1.49 ihickson 769: }
770:
771: function genkeys(p) {
772: var keys = _generateKeyPair();
773: p.postMessage(keys[0]);
774: p.postMessage(keys[1]);
775: }
776:
777: function encrypt(p) {
778: var key, state = 0;
779: p.onmessage = function (e) {
780: if (state == 0) {
1.54 ihickson 781: key = e.data;
1.49 ihickson 782: state = 1;
783: } else {
1.54 ihickson 784: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 785: }
786: };
787: }
788:
789: function decrypt(p) {
790: var key, state = 0;
791: p.onmessage = function (e) {
792: if (state == 0) {
1.54 ihickson 793: key = e.data;
1.49 ihickson 794: state = 1;
795: } else {
1.54 ihickson 796: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 797: }
798: };
799: }
800:
1.50 ihickson 801: // support being used as a shared worker as well as a dedicated worker
802: if (this.onmessage) // dedicated worker
803: onmessage = handleMessage;
804: else // shared worker
805: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 806:
807:
808: // the "crypto" functions:
809:
810: function _generateKeyPair() {
811: return [Math.random(), Math.random()];
812: }
813:
814: function _encrypt(k, s) {
815: return 'encrypted-' + k + ' ' + s;
816: }
817:
818: function _decrypt(k, s) {
819: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 820: }</pre><p>Note that the crypto functions here are just stubs and don't do
821: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
822: <html>
823: <head>
824: <title>Worker example: Crypto library</title>
825: <script>
1.50 ihickson 826: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 827: function getKeys() {
828: var state = 0;
1.50 ihickson 829: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 830: if (state == 0)
1.54 ihickson 831: document.getElementById('public').value = e.data;
1.49 ihickson 832: else if (state == 1)
1.54 ihickson 833: document.getElementById('private').value = e.data;
1.49 ihickson 834: state += 1;
835: };
836: }
837: function enc() {
1.50 ihickson 838: var port = cryptoLib.startConversation("encrypt");
839: port.postMessage(document.getElementById('public').value);
840: port.postMessage(document.getElementById('input').value);
841: port.onmessage = function (e) {
1.54 ihickson 842: document.getElementById('input').value = e.data;
1.50 ihickson 843: port.close();
1.49 ihickson 844: };
845: }
846: function dec() {
1.50 ihickson 847: var port = cryptoLib.startConversation("decrypt");
848: port.postMessage(document.getElementById('private').value);
849: port.postMessage(document.getElementById('input').value);
850: port.onmessage = function (e) {
1.54 ihickson 851: document.getElementById('input').value = e.data;
1.50 ihickson 852: port.close();
1.49 ihickson 853: };
854: }
1.81 ihickson 855: </script>
856: <style>
1.49 ihickson 857: textarea { display: block; }
1.81 ihickson 858: </style>
859: </head>
860: <body onload="getKeys()">
861: <fieldset>
862: <legend>Keys</legend>
863: <p><label>Public Key: <textarea id="public"></textarea></label></p>
864: <p><label>Private Key: <textarea id="private"></textarea></label></p>
865: </fieldset>
866: <p><label>Input: <textarea id="input"></textarea></label></p>
867: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
868: </body>
869: </html></pre><p>A later version of the API, though, might want to offload all the
870: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 871: if (e.data == "genkeys")
1.84 ihickson 872: genkeys(e.ports[0]);
1.54 ihickson 873: else if (e.data == "encrypt")
1.84 ihickson 874: encrypt(e.ports[0]);
1.54 ihickson 875: else if (e.data == "decrypt")
1.84 ihickson 876: decrypt(e.ports[0]);
1.49 ihickson 877: }
878:
879: function genkeys(p) {
1.50 ihickson 880: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 881: generator.postMessage('', [p]);
1.49 ihickson 882: }
883:
884: function encrypt(p) {
885: p.onmessage = function (e) {
1.54 ihickson 886: var key = e.data;
1.50 ihickson 887: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 888: encryptor.postMessage(key, [p]);
1.49 ihickson 889: };
890: }
891:
892: function encrypt(p) {
893: p.onmessage = function (e) {
1.54 ihickson 894: var key = e.data;
1.50 ihickson 895: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 896: decryptor.postMessage(key, [p]);
1.49 ihickson 897: };
898: }
899:
1.50 ihickson 900: // support being used as a shared worker as well as a dedicated worker
901: if (this.onmessage) // dedicated worker
902: onmessage = handleMessage;
903: else // shared worker
1.84 ihickson 904: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.81 ihickson 905: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 906: var k = _generateKeyPair();
1.84 ihickson 907: e.ports[0].postMessage(k[0]);
908: e.ports[0].postMessage(k[1]);
1.49 ihickson 909: close();
910: }
1.50 ihickson 911:
912: function _generateKeyPair() {
913: return [Math.random(), Math.random()];
1.81 ihickson 914: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 915: var key = e.data;
1.84 ihickson 916: e.ports[0].onmessage = function (e) {
1.54 ihickson 917: var s = e.data;
1.50 ihickson 918: postMessage(_encrypt(key, s));
1.49 ihickson 919: }
1.84 ihickson 920: e.ports[0].onclose = function (e) {
1.49 ihickson 921: close();
922: }
1.50 ihickson 923: }
924:
925: function _encrypt(k, s) {
926: return 'encrypted-' + k + ' ' + s;
1.81 ihickson 927: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 928: var key = e.data;
1.84 ihickson 929: e.ports[0].onmessage = function (e) {
1.54 ihickson 930: var s = e.data;
1.50 ihickson 931: postMessage(_decrypt(key, s));
1.49 ihickson 932: }
1.84 ihickson 933: e.ports[0].onclose = function (e) {
1.49 ihickson 934: close();
935: }
1.50 ihickson 936: }
937:
938: function _decrypt(k, s) {
939: return s.substr(s.indexOf(' ')+1);
1.81 ihickson 940: }</pre><p>Notice how the users of the API don't have to even know that this
941: is happening — the API hasn't changed; the library can
942: delegate to subworkers without changing its API, even though it is
1.82 ihickson 943: accepting data using message channels.<p><a href=http://www.whatwg.org/demos/workers/crypto/page.html>View this example online</a>.<h2 id=conformance-requirements><span class=secno>2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
1.81 ihickson 944: non-normative, as are all sections explicitly marked non-normative.
945: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
946: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
947: "OPTIONAL" in the normative parts of this document are to be
948: interpreted as described in RFC2119. For readability, these words do
949: not appear in all uppercase letters in this specification. <a href=#refsRFC2119>[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
950: (such as "strip any leading space characters" or "return false and
951: abort these steps") are to be interpreted with the meaning of the
952: key word ("must", "should", "may", etc) used in introducing the
953: algorithm.<p>Some conformance requirements are phrased as requirements on
954: attributes, methods or objects. Such requirements are to be
955: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
956: may be implemented in any manner, so long as the end result is
957: equivalent. (In particular, the algorithms defined in this
958: specification are intended to be easy to follow, and not intended to
959: be performant.)<p>The only conformance class defined by this specification is user
960: agents.<p>User agents may impose implementation-specific limits on
961: otherwise unconstrained inputs, e.g. to prevent denial of service
962: attacks, to guard against running out of memory, or to work around
1.82 ihickson 963: platform-specific limitations.<h3 id=dependencies><span class=secno>2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
1.81 ihickson 964: specifications.<dl><dt>HTML5</dt>
1.49 ihickson 965:
1.81 ihickson 966: <dd>
1.49 ihickson 967:
1.81 ihickson 968: <p>Many fundamental concepts from HTML5 are used by this
969: specification. <a href=#refsHTML5>[HTML5]</a></p>
1.49 ihickson 970:
1.81 ihickson 971: </dd>
1.1 ihickson 972:
1.81 ihickson 973: <dt>WebIDL</dt>
1.1 ihickson 974:
975: <dd>
976:
1.81 ihickson 977: <p>The IDL blocks in this specification use the semantics of the
978: WebIDL specification. <a href=#refsWebIDL>[WebIDL]</a></p>
1.1 ihickson 979:
1.81 ihickson 980: </dd>
1.1 ihickson 981:
1.82 ihickson 982: </dl><h2 id=terminology><span class=secno>3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 983: <code title="">Foo</code> is actually an interface, is sometimes
984: used instead of the more accurate "an object implementing the
985: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
986: scripts in Web applications, and does not necessarily imply the
987: existence of an actual <code>Document</code> object or of any other
988: <code>Node</code> objects as defined in the DOM Core
989: specifications. <a href=#refsDOM3CORE>[DOM3CORE]</a><p>A DOM attribute is said to be <em>getting</em> when its value is
990: being retrieved (e.g. by author script), and is said to be
1.82 ihickson 991: <em>setting</em> when a new value is assigned to it.<h2 id=infrastructure><span class=secno>4 </span>Infrastructure</h2><p>There are two kinds of workers; dedicated workers, and shared
1.81 ihickson 992: workers. Dedicated workers, once created, and are linked to their
993: creator; but message ports can be used to communicate from a
994: dedicated worker to multiple other browsing contexts or
995: workers. Shared workers, on the other hand, are named, and once
996: created any script running in the same <span>origin</span> can
1.82 ihickson 997: obtain a reference to that worker and communicate with it.<h3 id=the-global-scope><span class=secno>4.1 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id=the-workerglobalscope-abstract-interface><span class=secno>4.1.1 </span>The <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> abstract interface</h4><pre class=idl>interface <dfn id=workerglobalscope>WorkerGlobalScope</dfn> {
1.81 ihickson 998: readonly attribute <a href=#workerglobalscope>WorkerGlobalScope</a> <a href=#dom-workerglobalscope-self title=dom-WorkerGlobalScope-self>self</a>;
999: readonly attribute <a href=#workerlocation>WorkerLocation</a> <a href=#dom-workerglobalscope-location title=dom-WorkerGlobalScope-location>location</a>;
1000: // also implements everything on <a href=#workerutils>WorkerUtils</a>
1001:
1002: void <a href=#dom-workerglobalscope-close title=dom-WorkerGlobalScope-close>close</a>();
1003: attribute <span>EventListener</span> <a href=#handler-workerglobalscope-onclose title=handler-WorkerGlobalScope-onclose>onclose</a>;
1004: attribute <span>EventListener</span> <a href=#handler-workerglobalscope-onerror title=handler-WorkerGlobalScope-onerror>onerror</a>;
1005: };</pre><p>Objects implementing the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> interface
1006: must also implement the <code>EventTarget</code> interface.<p>The <dfn id=dom-workerglobalscope-self title=dom-WorkerGlobalScope-self><code>self</code></dfn> attribute
1007: must return the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object itself.<p>The <dfn id=dom-workerglobalscope-location title=dom-WorkerGlobalScope-location><code>location</code></dfn>
1008: attribute must return the <code><a href=#workerlocation>WorkerLocation</a></code> object created
1009: for the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object when the worker was
1010: created. It represents the <span>absolute URL</span> of the script
1011: that was used to initialize the worker.<hr><p>When a script invokes the <dfn id=dom-workerglobalscope-close title=dom-WorkerGlobalScope-close><code>close()</code></dfn> method on
1012: a <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object, the user agent must run the
1013: following steps:<ol><li><p><span>Queue a task</span> to <span>fire a simple
1014: event</span> called <code title=event-close>close</code> at the
1015: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</li>
1016:
1017: <li><p>Set the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object's
1018: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag to
1019: true.</li>
1020:
1021: <li><p>For each <code>MessagePort</code> object that is entangled
1022: with another port and that has one (but only one) port whose owner
1023: is the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object on which the method
1024: was invoked (this would include, for instance, the implicit port in
1025: used for dedicated workers), unentangle the two ports.</li>
1026:
1027: </ol><p>The following are the <span>event handler DOM attributes</span>
1028: that must be supported by objects implementing the
1029: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> interface:<dl><dt><dfn id=handler-workerglobalscope-onclose title=handler-WorkerGlobalScope-onclose><code>onclose</code></dfn></dt>
1030:
1031: <dd><p>Must be invoked whenever a <code title=event-close>close</code> event is targeted at or bubbles
1032: through the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</dd>
1.1 ihickson 1033:
1.50 ihickson 1034:
1.81 ihickson 1035: <dt><dfn id=handler-workerglobalscope-onerror title=handler-WorkerGlobalScope-onerror><code>onerror</code></dfn></dt>
1.50 ihickson 1036:
1.81 ihickson 1037: <dd><p>Must be invoked whenever an <code title=event-error>error</code> event is targeted at or bubbles
1038: through the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</dd>
1.50 ihickson 1039:
1.82 ihickson 1040: </dl><h4 id=dedicated-workers-and-the-dedicatedworkerglobalscope-interface><span class=secno>4.1.2 </span>Dedicated workers and the <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> interface</h4><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class=idl>[NoInterfaceObject, XXX] interface <dfn id=dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</dfn> : <a href=#workerglobalscope>WorkerGlobalScope</a> {
1.84 ihickson 1041: void <a href=#dom-dedicatedworkerglobalscope-postmessage title=dom-DedicatedWorkerGlobalScope-postMessage>postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1042: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.81 ihickson 1043: attribute <span>EventListener</span> <a href=#handler-dedicatedworkerglobalscope-onmessage title=handler-DedicatedWorkerGlobalScope-onmessage>onmessage</a>;
1044: };</pre><p><code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> objects act as if they
1045: had an implicit <code>MessagePort</code> associated with them. This
1046: port is part of a channel that is set up when the worker is created,
1047: but it is not exposed. This object must never be garbage collected
1048: before the <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be
1049: retargetted at the <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code>
1050: object.<p>The <dfn id=dom-dedicatedworkerglobalscope-postmessage title=dom-DedicatedWorkerGlobalScope-postMessage><code>postMessage()</code></dfn><!--
1.64 ihickson 1051: and <dfn
1052: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1053: method<!--s (startConversation)--> on
1054: <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1055: invoked, it<!--/they (startConversation)--> immediately invoked the
1056: method of the same name on the port, with the same arguments, and
1057: returned the same return value.<p>The following are the <span>event handler DOM attributes</span>
1058: that must be supported by objects implementing the
1059: <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> interface:<dl><dt><dfn id=handler-dedicatedworkerglobalscope-onmessage title=handler-DedicatedWorkerGlobalScope-onmessage><code>onmessage</code></dfn></dt>
1060:
1061: <dd><p>Must be invoked whenever a <code title=event-DedicatedWorkerGlobalScope-message>message</code> event is targeted
1062: at or bubbles through the <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object.</dd>
1063:
1.82 ihickson 1064: </dl><h4 id=shared-workers-and-the-sharedworkerglobalscope-inteface><span class=secno>4.1.3 </span>Shared workers and the <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> inteface</h4><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class=idl>[NoInterfaceObject, XXX] interface <dfn id=sharedworkerglobalscope>SharedWorkerGlobalScope</dfn> : <a href=#workerglobalscope>WorkerGlobalScope</a> {
1.81 ihickson 1065: readonly attribute DOMString <a href=#dom-sharedworkerglobalscope-name title=dom-SharedWorkerGlobalScope-name>name</a>;
1066: attribute <span>EventListener</span> <a href=#handler-sharedworkerglobalscope-onconnect title=handler-SharedWorkerGlobalScope-onconnect>onconnect</a>;
1067: };</pre><p>Shared workers receive message ports through <code title=event-WorkerGlobalScope-connect>connect</code> events on
1068: their global object for each connection.<p>The <dfn id=dom-sharedworkerglobalscope-name title=dom-SharedWorkerGlobalScope-name><code>name</code></dfn>
1069: attribute must return the value it was assigned when the
1070: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object was created by the
1071: "<a href=#run-a-worker>run a worker</a>" algorithm. Its value represents the name
1072: that can be used to obtain a reference to the worker using the
1073: <code><a href=#sharedworker>SharedWorker</a></code> constructor.<p>The following are the <span>event handler DOM attributes</span>
1074: that must be supported by objects implementing the
1075: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> interface:<dl><dt><dfn id=handler-sharedworkerglobalscope-onconnect title=handler-SharedWorkerGlobalScope-onconnect><code>onconnect</code></dfn></dt>
1076:
1077: <dd><p>Must be invoked whenever a <code title=event-SharedWorkerGlobalScope-connect>connect</code> event is targeted
1078: at or bubbles through the <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object.</dd>
1079:
1.82 ihickson 1080: </dl><h3 id=base-urls-and-origins-of-workers><span class=secno>4.2 </span>Base URLs and origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1081: origin</span> of scripts running in workers are the
1082: <span>origin</span> of the <span>absolute URL</span> given in that
1083: the worker's <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code> attribute
1.85 ihickson 1084: represents.<h3 id=decoding-scripts><span class=secno>4.3 </span>Decoding scripts</h3><p>When a user agent is to <dfn id=decode-a-script-resource>decode a script resource</dfn> to
1085: obtain its source in Unicode, it must run the following steps:<ol><li>
1086:
1087: <p>Let <var title="">character encoding</var> be <i title="">unknown</i>.</p>
1088:
1089: </li>
1090:
1091: <li>
1092:
1093: <p>For each of the rows in the following table, starting with the
1094: first one and going down, if the resource has as many or more
1095: bytes available than the number of bytes in the first column, and
1096: the first bytes of the resource match the bytes given in the first
1097: column, then let <var title="">character encoding</var> be the
1098: encoding given in the cell in the second column of that row:</p>
1099:
1100: <!-- this table is present in several forms in this file; keep them in sync -->
1101: <table><thead><tr><th>Bytes in Hexadecimal
1102: <th>Encoding
1103: <tbody><!-- nobody uses this
1104: <tr>
1105: <td>00 00 FE FF
1106: <td>UTF-32BE
1107: <tr>
1108: <td>FF FE 00 00
1109: <td>UTF-32LE
1110: --><tr><td>FE FF
1111: <td>UTF-16BE
1112: <tr><td>FF FE
1113: <td>UTF-16LE
1114: <tr><td>EF BB BF
1115: <td>UTF-8
1116: <!-- nobody uses this
1117: <tr>
1118: <td>DD 73 66 73
1119: <td>UTF-EBCDIC
1120: -->
1121: </table><p class=note>This step looks for Unicode Byte Order Marks
1122: (BOMs).</p>
1123:
1124: </li>
1125:
1126: <li>
1127:
1128: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, apply the <span>algorithm for extracting an
1129: encoding from a Content-Type</span> to the resource's <span title=Content-Type>Content Type metadata</span>; if this returns
1130: an encoding, and the user agent supports that encoding, then let
1131: <var title="">character encoding</var> be that encoding.</p>
1132:
1133: </li>
1134:
1135: <li>
1136:
1137: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, then let <var title="">character
1138: encoding</var> be UTF-8.</p>
1139:
1140: </li>
1141:
1142: <li>
1143:
1144: <p>Convert the resource to Unicode using the character encoding
1145: given by <var title="">character encoding</var>.</p>
1146:
1147: <p>Return the text that is so obtained.</p>
1148:
1149: </li>
1150:
1151: </ol><h3 id=the-event-loop><span class=secno>4.4 </span>The event loop</h3><p>Each <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object is asssociated with a
1.81 ihickson 1152: <span>event loop</span>. This <span>event loop</span> has no
1153: associated <span>browsing context</span>, and its <span title="task
1154: queue">task queues</span> only have events, callbacks, and
1155: networking activity as <span title=concept-task>tasks</span>. The
1156: processing model of these <span title="event loop">event
1157: loops</span> is defined below in the <a href=#run-a-worker>run a worker</a>
1158: algorithm.<p>Each <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object also has a <dfn id=dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</dfn> flag, which must
1159: initially be false, but which can get set to true by the algorithms
1160: in the processing model section below.<p>Once the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is set to
1161: true, the <span>event loop</span>'s <span title="task queue">task
1162: queues</span> must discard any further <span title=concept-task>tasks</span> that would be added to them (tasks
1163: already on the queue are unaffected unless otherwise
1164: specified). Effectively, once the <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is true,
1165: timers stop firing, notifications for all pending asynchronous
1.85 ihickson 1166: operations are dropped, etc.<h3 id=the-worker-s-ports><span class=secno>4.5 </span>The worker's ports</h3><p>Workers communicate with other workers and with <span title="browsing context">browsing contexts</span> through <span title="channel messaging">message channels</span> and their
1.81 ihickson 1167: <code>MessagePort</code> objects.<p>Each <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> <var title="">worker global
1168: scope</var> has a list of <dfn id=the-worker-s-ports-0>the worker's ports</dfn>, which
1169: consists of all the <code>MessagePort</code> objects that are
1170: entangled with another port and that have one (but only one) port
1171: owned by <var title="">worker global scope</var>. This list includes
1172: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1173: pending in the <span>event loop</span>, as well as (commented out
1174: because in practice it makes no difference either way as far as I
1175: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1176: ports might not yet be across the thread boundary)--> the implicit
1177: <code>MessagePort</code> in the case of <a href=#dedicatedworkerglobalscope title=DedicatedWorkerGlobalScope>dedicated workers</a>.<hr><p>A worker is said to be a <dfn id=permissible-worker>permissible worker</dfn> if
1178: either:<ul><li>at some point past or present a <code>MessagePort</code> owned
1179: by the worker was entangled with a <code>MessagePort</code> <var title="">p</var> whose owner is a <code>Window</code> object whose
1180: <span>active document</span> is the <code>Document</code> that was
1181: that <span>browsing context</span>'s <span>active document</span>
1182: when <var title="">p</var> was created, and that
1183: <code>Document</code> is <span>fully active</span>, or</li>
1184:
1185: <li>at some point past or present a <code>MessagePort</code> owned
1186: by the worker was entangled with a <code>MessagePort</code> owned
1187: by another worker that is currently a <a href=#permissible-worker>permissible
1188: worker</a>.</li>
1189:
1190: </ul><hr><p>A worker is said to be a <dfn id=protected-worker>protected worker</dfn> if
1191: either:<ul><li>it has outstanding timers, database transactions, or network
1192: connections, and is a <a href=#permissible-worker>permissible worker</a>, or</li>
1193:
1194: <li>there is a <a href=#protected-worker>protected worker</a> that at some point
1195: past or present owned a <code>MessagePort</code> that was entangled
1196: with a <code>MessagePort</code> owned by this worker.</li>
1197:
1198: </ul><hr><p>A worker is said to be an <dfn id=active-needed-worker>active needed worker</dfn> if either:
1199:
1200: <ul><li>the worker is a <a href=#protected-worker>protected worker</a>, or</li>
1201:
1202: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> is
1203: entangled with a <code>MessagePort</code> <var title="">p</var>
1204: whose owner is a <code>Window</code> object whose <span>active
1205: document</span> is the <code>Document</code> that was that
1206: <span>browsing context</span>'s <span>active document</span> when
1207: that <code>MessagePort</code> <var title="">p</var> was created,
1208: and that <code>Document</code> is <span>fully active</span>,
1209: or</li>
1210:
1211: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> has an
1212: entangled <code>MessagePort</code> owned by a
1213: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object that is itself an
1214: <a href=#active-needed-worker>active needed worker</a>.</li>
1215:
1216: </ul><hr><p>A worker is said to be a <dfn id=suspendable-worker>suspendable worker</dfn> if it is
1217: not an <a href=#active-needed-worker>active needed worker</a> but either:<ul><li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> has an
1218: entangled <code>MessagePort</code> owned by a <code>Window</code>
1219: object, or</li>
1220:
1221: <li>at least one of the <a href=#the-worker-s-ports-0>the worker's ports</a> has an
1222: entangled <code>MessagePort</code> owned by a
1223: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object that is itself a <span>needed
1224: worker</span>.</li>
1225:
1.85 ihickson 1226: </ul><h3 id=processing-model><span class=secno>4.6 </span>Processing model</h3><p>When a user agent is to <dfn id=run-a-worker>run a worker</dfn> for a script with
1.81 ihickson 1227: <span>URL</span> <var title="">url</var>, a browsing context <var title="">owner browsing context</var>, and with global scope <var title="">worker global scope</var>, it must run the following
1228: steps:<ol><li>
1229:
1230: <p>Create a completely separate and parallel execution environment
1231: (i.e. a separate thread or process or equivalent construct), and
1232: run the rest of these steps asychronously in that context.</p>
1233:
1234: </li>
1.4 ihickson 1235:
1236: <li>
1.52 ihickson 1237:
1.81 ihickson 1238: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>.</p>
1239:
1240: <p>If the attempt fails, then for each <code><a href=#worker>Worker</a></code> or
1241: <code><a href=#sharedworker>SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1242: <span>fire a simple event</span> called <code title=event-error>error</code> at that object. Abort these
1243: steps.</p>
1.7 ihickson 1244:
1.85 ihickson 1245: <p>If the attempt succeeds, then <a href=#decode-a-script-resource title="decode a script
1246: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1.81 ihickson 1247:
1.68 ihickson 1248: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1249:
1.81 ihickson 1250: <p class=note>As with <code>script</code> elements, the MIME
1251: type of the script is ignored. Unlike with <code>script</code>
1252: elements, there is no way to override the type. It's always
1253: assumed to be JavaScript.</p> <!-- XXX people will complain about
1.7 ihickson 1254: this. I guess we might want to examine the MIME type... -->
1.81 ihickson 1255:
1256: </li>
1.7 ihickson 1257:
1258: <li>
1.68 ihickson 1259:
1.81 ihickson 1260: <p>A new <span title=concept-script>script</span> is now
1261: created, as follows.</p>
1262:
1263: <p>Create a new <span>script execution environment</span>
1264: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1265:
1.68 ihickson 1266: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1267: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1268: entry-points</span>; set the <i>initial code entry-point</i> to
1269: the entry-point for any executable code to be immediately run.</p>
1270:
1271: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1272:
1273: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1274:
1.83 ihickson 1275: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1276: UTF-8. (This is just used for encoding non-ASCII characters in the
1277: query component of URLs.)</p>
1.68 ihickson 1278:
1279: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1280:
1.81 ihickson 1281: <p>Create a new <span>script group</span> and add the <span title=concept-script>script</span> to it.</p>
1282:
1283: </li>
1.4 ihickson 1284:
1285: <li>
1.81 ihickson 1286:
1287: <p><strong>Closing orphan workers</strong>: Start monitoring the
1288: worker such that as soon as it stops being either an <a href=#active-needed-worker>active
1289: needed worker</a> or a <a href=#suspendable-worker>suspendable worker</a>, <var title="">worker global scope</var>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is set
1290: to true and <span title="queue a task">a task is queued</span> to
1291: <span>fire a simple event</span> called <code title=event-close>close</code> at <var title="">worker global
1292: scope</var>.</p>
1293:
1294: </li>
1.9 ihickson 1295:
1296: <li>
1.7 ihickson 1297:
1.81 ihickson 1298: <p><strong>Suspending workers</strong>: Start monitoring the
1299: worker, such that whenever <var title="">worker global
1300: scope</var>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is false
1301: and the worker is a <a href=#suspendable-worker>suspendable worker</a>, the user
1302: agent suspends execution of script in that worker until such time
1303: as either the <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag switches
1304: to true or the worker stops being a <a href=#suspendable-worker>suspendable
1305: worker</a>.</p>
1.4 ihickson 1306:
1.81 ihickson 1307: </li>
1.68 ihickson 1308:
1309: <li>
1.4 ihickson 1310:
1.81 ihickson 1311: <p><span title="jump to a code entry-point">Jump</span> to the
1312: <span title=concept-script>script</span>'s <i>initial code
1313: entry-point</i>, and let that run until it either returns, fails
1314: to catch an exception, or gets prematurely aborted by the
1315: "<a href=#kill-a-worker>kill a worker</a>" or "<a href=#terminate-a-worker>terminate a worker</a>"
1316: algorithms defined below.</p>
1317:
1318: <p class=note>If the script gets aborted by the "<a href=#kill-a-worker>kill a
1319: worker</a>" algorithm, then that same algorithm will cause
1320: there to only be a single <span title=concept-task>task</span>
1321: in the <span>event loop</span> at the next step, namely the task
1322: for the <code title=message-close>close</code> event. The
1323: "<a href=#terminate-a-worker>terminate a worker</a>" algorithm removes all the
1324: events.</p>
1.4 ihickson 1325:
1.81 ihickson 1326: </li>
1.4 ihickson 1327:
1328: <li>
1.68 ihickson 1329:
1.81 ihickson 1330: <p><i title="">Event loop</i>: Wait until either there is a <span title=concept-task>task</span> in one of the <span>event
1331: loop</span>'s <span title="task queue">task queues</span> or <var title="">worker global scope</var>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is set
1332: to true.</p>
1.43 ihickson 1333:
1.81 ihickson 1334: </li>
1.4 ihickson 1335:
1336: <li>
1337:
1.81 ihickson 1338: <p>Run the oldest task on one of the <span>event loop</span>'s
1339: <span title="task queue">task queues</span>, if any. The user
1340: agent may pick any <span>task queue</span>.</p>
1341:
1342: <p class=note>The handling of events or the execution of
1343: callbacks might get prematurely aborted by the "<a href=#kill-a-worker>kill a
1344: worker</a>" or "<a href=#terminate-a-worker>terminate a worker</a>" algorithms
1345: defined below.</p>
1.8 ihickson 1346:
1.81 ihickson 1347: </li>
1.4 ihickson 1348:
1349: <li>
1350:
1.81 ihickson 1351: <p>Remove the task run in the previous step, if any, from its
1352: <span>task queue</span>.</p>
1.4 ihickson 1353:
1.81 ihickson 1354: </li>
1.4 ihickson 1355:
1356: <li>
1.8 ihickson 1357:
1.81 ihickson 1358: <p>If there are any more events in the <span>event loop</span>'s
1359: <span title="task queue">task queues</span> or if <var title="">worker global scope</var>'s <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is set
1360: to false, then jump back to the step above labeled <i>event
1361: loop</i>.</p>
1.8 ihickson 1362:
1.81 ihickson 1363: </li>
1.8 ihickson 1364:
1365: <li>
1.71 ihickson 1366:
1.81 ihickson 1367: <p>Freeze the <span>script group</span>.</p>
1.50 ihickson 1368:
1.81 ihickson 1369: <p class=note>This kills timers, database transactions, etc.</p>
1.50 ihickson 1370:
1.81 ihickson 1371: </li>
1.50 ihickson 1372:
1.81 ihickson 1373: <li>
1.50 ihickson 1374:
1.81 ihickson 1375: <p>For each <code><a href=#worker>Worker</a></code> or <code><a href=#sharedworker>SharedWorker</a></code>
1376: object associated with <var title="">worker global scope</var>,
1377: <span>queue a task</span> to <span>fire a simple event</span>
1378: called <code title=event-close>close</code> at that object.</p>
1.5 ihickson 1379:
1.81 ihickson 1380: </li>
1.50 ihickson 1381:
1.81 ihickson 1382: </ol><hr><p>When a user agent is to <dfn id=kill-a-worker>kill a worker</dfn> it must
1383: run the following steps in parallel with the worker's main loop (the
1384: "<a href=#run-a-worker>run a worker</a>" processing model defined above):<ol><li><p>If the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object's
1385: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag is
1386: false, <span>queue a task</span> to <span>fire a simple
1387: event</span> called <code title=event-close>close</code> at the
1388: worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object.</li>
1389:
1390: <li><p>Set the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object's <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag to
1391: true.</li>
1392:
1393: <li><p>Wait a user-agent-defined amount of time. If the "<a href=#run-a-worker>run
1394: a worker</a>" processing model defined above immediately starts
1395: running event listeners registered for the <code title=event-close>close</code> event, this time should not be
1396: zero — the idea is that the <code title=event-close>close</code> event can be used to clean up
1397: when shutting down unexpectedly.</li>
1398:
1399: <li><p>If there are any <span title=concept-task>tasks</span>
1400: queued in the <span>event loop</span>'s <span title="task
1401: queue">task queues</span> other than the <code title=event-close>close</code> event that this algorithm just
1402: added, discard them without processing them.</li>
1403:
1404: <li><p>If the <code title=event-close>close</code> event that
1405: this algorithm just queued hasn't yet been dispatched, then abort
1406: the script currently running in the worker.</li>
1407:
1408: <li><p>Wait a user-agent-defined amount of time.</li>
1409:
1410: <li><p>Abort the script currently running in the worker (if any
1411: script is running, then it will be a handler for the <code title=event-close>close</code> event).</li>
1412:
1413: </ol><p>User agents may invoke the "<a href=#kill-a-worker>kill a worker</a>"
1414: processing model on a worker at any time, e.g. in response to user
1415: requests, in response to CPU quota management, or when a worker
1416: stops being an <a href=#active-needed-worker>active needed worker</a> if the worker
1417: continues executing even after its <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag was
1418: set to true.<hr><p>When a user agent is to <dfn id=terminate-a-worker>terminate a worker</dfn> it must run
1419: the following steps in parallel with the worker's main loop (the
1420: "<a href=#run-a-worker>run a worker</a>" processing model defined above):<ol><li><p>Set the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object's
1421: <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a> flag to
1422: true.</li>
1423:
1424: <li><p>If there are any <span title=concept-task>tasks</span>
1425: queued in the <span>event loop</span>'s <span title="task
1426: queue">task queues</span>, discard them without processing
1427: them.</li>
1428:
1429: <li><p>Abort the script currently running in the worker.</li>
1430:
1431: <li><p>If the worker's <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object is
1432: actually a <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code> object (i.e. the
1433: worker is a dedicated worker), then empty the <span>port message
1434: queue</span> of the port that the worker's implicit port is
1435: entangled with.</li>
1436:
1.85 ihickson 1437: </ol><h4 id=runtime-script-errors><span class=secno>4.6.1 </span>Runtime script errors</h4><p>Whenever a runtime script error occurs in one of the worker's
1.81 ihickson 1438: scripts, if the error did not occur while handling a previous script
1439: error, the user agent must <span>queue a task</span> to <a href=#fire-an-error-event>fire
1440: an error event</a> at the the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code>
1441: object.<p>For shared workers, if the error is still <i title="">not
1442: handled</i> afterwards, or if the error occured while handling a
1443: previous script error, the error should be reported to the user.<p>For dedicated workers, if the error is still <i title="">not
1444: handled</i> afterwards, or if the error occured while handling a
1445: previous script error, the user agent must further <span>queue a
1446: task</span> to <a href=#fire-an-error-event>fire an error event</a> at the
1447: <code><a href=#worker>Worker</a></code> object associated with the worker.<p>When the user agent is to <dfn id=fire-an-error-event>fire an error event</dfn> at a
1448: <code><a href=#worker>Worker</a></code> object, it must dispatch an event that uses the
1449: <code><a href=#errorevent>ErrorEvent</a></code> interface, with the name <code title=event-error>error</code>, that doesn't bubble and is
1450: cancelable, with its <code title=dom-ErrorEvent-message><a href=#dom-errorevent-message>message</a></code>, <code title=dom-ErrorEvent-filename><a href=#dom-errorevent-filename>filename</a></code>, and <code title=dom-ErrorEvent-lineno><a href=#dom-errorevent-lineno>lineno</a></code> attributes set
1451: appropriately. The default action of this event depends on whether
1452: the <code><a href=#worker>Worker</a></code> object is itself in a worker. If it is, and
1453: that worker is also a dedicated worker, then the user agent must
1454: again <span>queue a task</span> to <a href=#fire-an-error-event>fire an error event</a>
1455: at the <code><a href=#worker>Worker</a></code> object associated with <em>that</em>
1456: worker. Otherwise, then the error should be reported to the
1457: user.<hr><pre class=idl>interface <dfn id=errorevent>ErrorEvent</dfn> : Event {
1458: readonly attribute DOMObject <a href=#dom-errorevent-message title=dom-ErrorEvent-message>message</a>;
1459: readonly attribute DOMObject <a href=#dom-errorevent-filename title=dom-ErrorEvent-filename>filename</a>;
1460: readonly attribute unsigned long <a href=#dom-errorevent-lineno title=dom-ErrorEvent-lineno>lineno</a>;
1461: void <a href=#dom-errorevent-initerrorevent title=dom-ErrorEvent-initErrorEvent>initErrorEvent</a>(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMObject messageArg, in DOMObject filenameArg, in unsigned long linenoArg);
1462: void <a href=#dom-errorevent-initerroreventns title=dom-ErrorEvent-initErrorEventNS>initErrorEventNS</a>(in DOMString namespaceURIArg, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMObject messageArg, in DOMObject filenameArg, in unsigned long linenoArg);
1463: };</pre><p>The <dfn id=dom-errorevent-initerrorevent title=dom-ErrorEvent-initErrorEvent><code>initErrorEvent()</code></dfn>
1464: and <dfn id=dom-errorevent-initerroreventns title=dom-ErrorEvent-initErrorEventNS><code>initErrorEventNS()</code></dfn>
1465: methods must initialize the event in a manner analogous to the
1466: similarly-named methods in the DOM3 Events interfaces. <a href=#refsDOM3EVENTS>[DOM3EVENTS]</a><p>The <dfn id=dom-errorevent-message title=dom-ErrorEvent-message><code>message</code></dfn>
1467: attribute represents the error message.<p>The <dfn id=dom-errorevent-filename title=dom-ErrorEvent-filename><code>filename</code></dfn>
1468: attribute represents the <span>absolute URL</span> of the script in
1469: which the error originally occured.<p>The <dfn id=dom-errorevent-lineno title=dom-ErrorEvent-lineno><code>lineno</code></dfn>
1470: attribute represents the line number where the error occured in the
1.85 ihickson 1471: script.<h3 id=creating-workers><span class=secno>4.7 </span>Creating workers</h3><h4 id=the-abstractworker-abstract-interface><span class=secno>4.7.1 </span>The <code><a href=#abstractworker>AbstractWorker</a></code> abstract interface</h4><pre class=idl>interface <dfn id=abstractworker>AbstractWorker</dfn> {
1.81 ihickson 1472: attribute <span>EventListener</span> <a href=#handler-abstractworker-onerror title=handler-AbstractWorker-onerror>onerror</a>;
1473: attribute <span>EventListener</span> <a href=#handler-abstractworker-onclose title=handler-AbstractWorker-onclose>onclose</a>;
1474: };</pre><p>Objects implementing the <code><a href=#abstractworker>AbstractWorker</a></code> interface
1475: must also implement the <code>EventTarget</code> interface.<p>The following are the <span>event handler DOM attributes</span>
1476: that must be supported by objects implementing the
1477: <code><a href=#abstractworker>AbstractWorker</a></code> interface:<dl><dt><dfn id=handler-abstractworker-onerror title=handler-AbstractWorker-onerror><code>onerror</code></dfn></dt>
1478:
1479: <dd><p>Must be invoked whenever an <code title=event-error>error</code> event is targeted at or bubbles
1480: through the <code><a href=#abstractworker>AbstractWorker</a></code> object.</dd>
1481:
1482: <dt><dfn id=handler-abstractworker-onclose title=handler-AbstractWorker-onclose><code>onclose</code></dfn></dt>
1483:
1484: <dd><p>Must be invoked whenever an <code title=event-close>close</code> event is targeted at or bubbles
1485: through the <code><a href=#abstractworker>AbstractWorker</a></code> object.</dd>
1486:
1.85 ihickson 1487: </dl><h4 id=dedicated-workers-and-the-worker-interface><span class=secno>4.7.2 </span>Dedicated workers and the <code><a href=#worker>Worker</a></code> interface</h4><pre class=idl>[<a href=#dom-worker title=dom-Worker>Constructor</a>(in DOMString scriptURL)]
1.81 ihickson 1488: interface <dfn id=worker>Worker</dfn> : <a href=#abstractworker>AbstractWorker</a> {
1489: void <a href=#dom-worker-terminate title=dom-Worker-terminate>terminate</a>();
1.50 ihickson 1490:
1.84 ihickson 1491: void <a href=#dom-worker-postmessage title=dom-Worker-postMessage>postMessage</a>(in any message, [Optional] in <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1492: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1493: attribute <span>EventListener</span> <a href=#handler-worker-onmessage title=handler-Worker-onmessage>onmessage</a>;
1494: };</pre><p>The <dfn id=dom-worker-terminate title=dom-Worker-terminate><code>terminate()</code></dfn> method,
1495: when invoked, must cause the "<a href=#terminate-a-worker>terminate a worker</a>"
1496: algorithm to be run on the worker with with the object is
1497: associated.<p><code><a href=#worker>Worker</a></code> objects act as if they had an implicit
1498: <code>MessagePort</code> associated with them. This port is part of
1499: a channel that is set up when the worker is created, but it is not
1500: exposed. This object must never be garbage collected before the
1501: <code><a href=#worker>Worker</a></code> object.<p>All messages received by that port must immediately be
1502: retargetted at the <code><a href=#worker>Worker</a></code> object.<p>The <dfn id=dom-worker-postmessage title=dom-Worker-postMessage><code>postMessage()</code></dfn><!--
1.64 ihickson 1503: and <dfn
1504: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1505: method<!--s (startConversation)--> on <code><a href=#worker>Worker</a></code> objects
1506: must act as if, when invoked, it<!--/they (startConversation)-->
1507: immediately invoked the method of the same name on the port, with
1508: the same arguments, and returned the same return value.<p>The following are the <span>event handler DOM attributes</span>
1509: that must be supported by objects implementing the
1510: <code><a href=#worker>Worker</a></code> interface:<dl><dt><dfn id=handler-worker-onmessage title=handler-Worker-onmessage><code>onmessage</code></dfn></dt>
1511:
1512: <dd><p>Must be invoked whenever a <code title=event-Worker-message>message</code> event is targeted
1513: at or bubbles through the <code><a href=#worker>Worker</a></code> object.</dd>
1.50 ihickson 1514:
1.81 ihickson 1515: </dl><hr><p>When the <dfn id=dom-worker title=dom-Worker><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1516: user agent must run the following steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.9 ihickson 1517:
1.81 ihickson 1518: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1519: exception.</li>
1.9 ihickson 1520:
1.81 ihickson 1521: <li><p>If the <span>origin</span> of the resulting <span>absolute
1522: URL</span> is not the <span title="same origin">same</span> as the
1523: origin of the script that invoked the constructor, then throw a
1524: <span>security exception</span>.</li>
1.9 ihickson 1525:
1.81 ihickson 1526: <li><p><span>Create a new <code><a href=#dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</a></code>
1527: object</span>. Let <var title="">worker global scope</var> be this
1528: new object.</li>
1.9 ihickson 1529:
1.81 ihickson 1530: <li><p>Create a new <code><a href=#worker>Worker</a></code> object, associated with
1531: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1532:
1.81 ihickson 1533: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1534: by the <span>script execution context</span> of the script that
1535: invoked the method. Let this be the <var title="">outside
1536: port</var>.</li>
1.9 ihickson 1537:
1.81 ihickson 1538: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1539:
1.81 ihickson 1540: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1541: by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1542:
1.81 ihickson 1543: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1544:
1.81 ihickson 1545: <li><p><span>Entangle</span> <var title="">outside port</var> and
1546: <var title="">inside port</var>.</li>
1.50 ihickson 1547:
1.81 ihickson 1548: <li><p>Return <var title="">worker</var>, and run the following
1549: steps asynchronously.</li>
1.50 ihickson 1550:
1.81 ihickson 1551: <li><p>Open <var title="">inside port</var>'s <span>port message
1552: queue</span>.</li>
1.50 ihickson 1553:
1.81 ihickson 1554: <li><p>Open <var title="">outside port</var>'s <span>port message
1555: queue</span>.</li>
1.50 ihickson 1556:
1557: <li>
1.51 ihickson 1558:
1.81 ihickson 1559: <p><a href=#run-a-worker>Run a worker</a> for the resulting <span>absolute
1560: URL</span>, with the <span>script browsing context</span> of the
1561: script that invoked the method as the <var title="">owner browsing
1562: context</var>, and with <var title="">worker global scope</var> as
1563: the global scope.</p>
1.9 ihickson 1564:
1.81 ihickson 1565: </li>
1.4 ihickson 1566:
1.85 ihickson 1567: </ol><h4 id=shared-workers-and-the-sharedworker-interface><span class=secno>4.7.3 </span>Shared workers and the <code><a href=#sharedworker>SharedWorker</a></code> interface</h4><pre class=idl>[<a href=#dom-sharedworker title=dom-SharedWorker>Constructor</a>(in DOMString scriptURL, in DOMString name)]
1.81 ihickson 1568: interface <dfn id=sharedworker>SharedWorker</dfn> : <a href=#abstractworker>AbstractWorker</a> {
1569: readonly attribute <span>MessagePort</span> <a href=#dom-sharedworker-port title=dom-SharedWorker-port>port</a>;
1570: };</pre><p>The <dfn id=dom-sharedworker-port title=dom-SharedWorker-port><code>port</code></dfn>
1571: attribute must return the value it was assigned by the object's
1572: constructor. It represents the <code>MessagePort</code> for
1573: communicating with the shared worker.<p>When the <dfn id=dom-sharedworker title=dom-SharedWorker><code>SharedWorker(<var title="">scriptURL</var>, <var title="">name</var>)</code></dfn>
1574: constructor is invoked, the user agent must run the following
1575: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1576:
1577: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1578: exception.</li>
1579:
1580: <li><p>If the <span>origin</span> of the resulting <span>absolute
1581: URL</span> is not the <span title="same origin">same</span> as the
1582: origin of the script that invoked the constructor, then throw a
1583: <span>security exception</span>.</li>
1.9 ihickson 1584:
1585: <li>
1586:
1.50 ihickson 1587: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1588:
1.81 ihickson 1589: <ol><li><p>Create a new <code><a href=#sharedworker>SharedWorker</a></code> object, which will
1590: shortly be associated with a <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code>
1591: object. Let this <code><a href=#sharedworker>SharedWorker</a></code> object be <var title="">worker</var>.</li>
1592:
1593: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1594: by the <span>script execution context</span> of the script that
1595: invoked the method. Let this be the <var title="">outside
1596: port</var>.</li>
1597:
1598: <li><p>Assign <var title="">outside port</var> to the <code title=dom-SharedWorker-port><a href=#dom-sharedworker-port>port</a></code> attribute of <var title="">worker</var>.</li>
1599:
1.9 ihickson 1600: <li>
1601:
1.81 ihickson 1602: <p>If there exists a <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object
1603: whose <a href=#dom-workerglobalscope-closing title=dom-WorkerGlobalScope-closing>closing</a>
1604: flag is false, whose <code title=dom-WorkerGlobalScope-name>name</code> attribute is
1605: exactly equal to the <var title="">name</var> argument, and
1606: whose <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code> attribute
1607: represents an <span>absolute URL</span> that has the <span>same
1608: origin</span> as the resulting <span>absolute URL</span>, then
1609: run these substeps:</p>
1610:
1611: <ol><li><p>Let <var title="">worker global scope</var> be that
1612: <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code> object.</li>
1613:
1614: <li><p>If <var title="">worker global scope</var>'s <code title=dom-WorkerGlobalScope-location><a href=#dom-workerglobalscope-location>location</a></code>
1615: attribute represents an <span>absolute URL</span> that is not
1616: exactly equal to the resulting <span>absolute URL</span>, then
1617: throw a <code>URL_MISMATCH_ERR</code> exception and abort all
1.82 ihickson 1618: these steps. <span class=XXX>code 21</span></li>
1.81 ihickson 1619:
1620: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1621:
1622: <li><p><span>Create a <code>MessagePort</code> object</span>
1623: owned by <var title="">worker global scope</var>. Let this
1624: be the <var title="">inside port</var>.</li>
1625:
1626: <li><p><span>Entangle</span> <var title="">outside port</var>
1627: and <var title="">inside port</var>.</li>
1628:
1629: <li><p>Return <var title="">worker</var> and perform the next
1630: step asynchronously.</li>
1.9 ihickson 1631:
1.81 ihickson 1632: <li><p>Create an event that uses the <code>MessageEvent</code>
1633: interface, with the name <code title=event-connect>connect</code>, which does not bubble, is
1634: cancelable, has no default action, has a <code title=dom-MessageEvent-data>data</code> attribute whose value
1.84 ihickson 1635: is the empty string and has a <code title=dom-MessageEvent-ports>ports</code>
1636: attribute whose value is an array containing only the newly
1637: created port, and <span>queue a task</span> to dispatch the
1638: event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1639:
1.81 ihickson 1640: <li><p>Abort all these steps.</li>
1.9 ihickson 1641:
1.81 ihickson 1642: </ol></li>
1.9 ihickson 1643:
1.81 ihickson 1644: <li><p><span>Create a new <code><a href=#sharedworkerglobalscope>SharedWorkerGlobalScope</a></code>
1645: object</span>. Let <var title="">worker global scope</var> be
1646: this new object.</li>
1.9 ihickson 1647:
1.81 ihickson 1648: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1649:
1.81 ihickson 1650: <li><p>Set the <code title=dom-SharedWorkerGlobalScope-name><a href=#dom-sharedworkerglobalscope-name>name</a></code> attribute of
1651: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1652:
1.81 ihickson 1653: <li><p><span>Create a <code>MessagePort</code> object</span>
1654: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1655:
1.81 ihickson 1656: <li><p><span>Entangle</span> <var title="">outside port</var> and
1657: <var title="">inside port</var>.</li>
1.9 ihickson 1658:
1.81 ihickson 1659: </ol></li>
1.28 ihickson 1660:
1.81 ihickson 1661: <li><p>Return <var title="">worker</var> and perform the next step
1662: asynchronously.</li>
1.18 ihickson 1663:
1.81 ihickson 1664: <li><p>Create an event that uses the <code>MessageEvent</code>
1665: interface, with the name <code title=event-connect>connect</code>, which does not bubble, is
1666: cancelable, has no default action, has a <code title=dom-MessageEvent-data>data</code> attribute whose value is
1.84 ihickson 1667: the empty string and has a <code title=dom-MessageEvent-ports>ports</code> attribute
1668: whose value is an array containing only the newly created port, and
1669: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.26 ihickson 1670:
1671: <li>
1.46 ihickson 1672:
1.81 ihickson 1673: <p><a href=#run-a-worker>Run a worker</a> for the resulting <span>absolute
1674: URL</span>, with the <span>script browsing context</span> of the
1675: script that invoked the method as the <var title="">owner browsing
1676: context</var>, and with <var title="">worker global scope</var> as
1677: the global scope.</p>
1.26 ihickson 1678:
1.60 ihickson 1679: </li>
1.81 ihickson 1680:
1.82 ihickson 1681: </ol><h2 id=apis-available-to-workers><span class=secno>5 </span>APIs available to workers</h2><!-- the XXX below is for collapsing this interface onto WorkerGlobalScope so it looks like just one interface - the inheritance is a spec fiction only --><pre class=idl>[NoInterfaceObject, ImplementedOn=WorkerGlobalScope, XXX] interface <dfn id=workerutils>WorkerUtils</dfn> {
1.81 ihickson 1682: void <a href=#dom-workerglobalscope-importscripts title=dom-WorkerGlobalScope-importScripts>importScripts</a>([Variadic] in DOMString urls);
1.93 ! ihickson 1683: readonly attribute <a href=#worker-navigator title=worker-Navigator>Navigator</a> <a href=#dom-worker-navigator title=dom-worker-navigator>navigator</a>;
1.92 ihickson 1684: <span>Database</span> <a href=#dom-opendatabase title=dom-opendatabase>openDatabase</a>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
1.81 ihickson 1685: };</pre><p>Objects that implement the <code><a href=#workerglobalscope>WorkerGlobalScope</a></code>
1686: interface must also implement the <code><a href=#workerutils>WorkerUtils</a></code>
1687: interface.<p>Objects that implement the <code><a href=#workerutils>WorkerUtils</a></code> interface
1688: must also implement the <code>WindowTimers</code> interface. (This
1689: interface provides the <code title="">setTimeout()</code> method and
1.82 ihickson 1690: its friends.)<p class=XXX>Need to define a sync database API.</p><!-- XXX ApplicationCache --><!-- XXX a way to set cookies on the URL for the script --><!-- XXX debugging: void log(in DOMString s); // log to console --><!-- XXX debugging: onerror --><hr><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1691: objects, etc) are not available to workers in this version of this
1.82 ihickson 1692: specification.<h3 id=importing-scripts-and-libraries><span class=secno>5.1 </span>Importing scripts and libraries</h3><p>When a script invokes the <dfn id=dom-workerglobalscope-importscripts title=dom-WorkerGlobalScope-importScripts><code>importScripts(<var title="">urls</var>)</code></dfn> method on a
1.81 ihickson 1693: <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object, the user agent must run the
1694: following steps:<ol><li><p>If there are no arguments, return without doing
1695: anything. Abort these steps.</li>
1696:
1697: <li><p><span title="resolve a url">Resolve</span> each
1698: argument.</li>
1699:
1700: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1701: exception.</li>
1702:
1703: <!--
1.67 ihickson 1704: <li><p>If any of the resulting <span title="absolute URL">absolute
1705: URLs</span> have an <span>origin</span> that is not the <span
1706: title="same origin">same</span> as the origin of the script that
1707: invoked the method, then throw a <span>security
1708: exception</span>.</p></li>
1709: -->
1.26 ihickson 1710:
1711: <li>
1.81 ihickson 1712:
1.45 ihickson 1713: <p>Attempt to <span>fetch</span> each resource identified by the
1.81 ihickson 1714: resulting <span title="absolute URLs">absolute URL</span>.</p>
1715:
1716: </li>
1.26 ihickson 1717:
1718: <li>
1719:
1.81 ihickson 1720: <p>For each argument in turn, in the order given, starting with
1721: the first one, run these substeps:</p>
1.26 ihickson 1722:
1.81 ihickson 1723: <ol><li>
1.26 ihickson 1724:
1.81 ihickson 1725: <p>Wait for the fetching attempt for the corresponding resource
1726: to complete.</p>
1.60 ihickson 1727:
1.81 ihickson 1728: <p>If the fetching attempt failed, throw a
1729: <code>NETWORK_ERR</code> exception and abort all these
1730: steps.</p>
1.45 ihickson 1731:
1.85 ihickson 1732: <p>If the attempt succeeds, then <a href=#decode-a-script-resource title="decode a script
1733: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1734:
1735: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1736:
1.81 ihickson 1737: <p class=note>As with the worker's script, the script here is
1738: always assumed to be JavaScript, regardless of the MIME
1739: type.</p> <!-- XXX -->
1.61 ihickson 1740:
1.81 ihickson 1741: </li>
1.26 ihickson 1742:
1.81 ihickson 1743: <li>
1.26 ihickson 1744:
1.81 ihickson 1745: <p><span>Create a script</span>, using <var title="">source</var> as the script source and <var title="">language</var> as the scripting language, using the
1746: same global object, browsing context, character encoding, base
1747: URL, and script group as the <span title=concept-script>script</span> that was created by the
1748: worker's <a href=#run-a-worker>run a worker</a> algorithm.</p>
1749:
1750: <p>Let the newly created <span title=concept-script>script</span> run until it either
1751: returns, fails to parse, fails to catch an exception, or gets
1752: prematurely aborted by the "<a href=#kill-a-worker>kill a worker</a>" or
1753: "<a href=#terminate-a-worker>terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1754:
1.81 ihickson 1755: <p>If it failed to parse, then throw a
1756: <code>SyntaxError</code><!-- XXX ref? --> exception and abort
1757: all these steps.</p>
1.63 ihickson 1758:
1.81 ihickson 1759: <p>If an exception was raised or if the script was prematurely
1760: aborted, then abort all these steps, letting the exception or
1761: aborting continue to be processed by the script that called the
1762: <code title=dom-WorkerGlobalScope-importScripts><a href=#dom-workerglobalscope-importscripts>importScripts()</a></code>
1763: method.</p>
1764:
1765: <p>If the "<a href=#kill-a-worker>kill a worker</a>" or "<a href=#terminate-a-worker>terminate a
1766: worker</a>" algorithms abort the script then abort all these
1767: steps.</p>
1768:
1769: </li>
1770:
1771: </ol></li>
1772:
1.93 ! ihickson 1773: </ol><h3 id=the-navigator-object><span class=secno>5.2 </span>The <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code> object</h3><p>The <dfn id=dom-worker-navigator title=dom-worker-navigator><code>navigator</code></dfn> attribute
! 1774: of the <code><a href=#workerutils>WorkerUtils</a></code> interface must return an instance of
! 1775: the <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code> interface, which
! 1776: represents the identity and state of the user agent (the
! 1777: client):<pre class=idl>interface <dfn id=worker-navigator title=worker-Navigator>Navigator</dfn> {
1.81 ihickson 1778: // objects implementing this interface also implement the interfaces listed below
1.93 ! ihickson 1779: };</pre><p>Objects implementing the <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code> interface must also
! 1780: implement the <span>NavigatorID</span> and
1.81 ihickson 1781: <span>NavigatorOnLine</span> interfaces specified in the HTML5
1.93 ! ihickson 1782: specification. <a href=#refsHTML5>[HTML5]</a><p class=note>The <code title=worker-Navigator><a href=#worker-navigator>Navigator</a></code>
! 1783: interface defined in this specification is different than the one
! 1784: defined in the HTML5 specification.<h3 id=apis-defined-in-other-specifications><span class=secno>5.3 </span>APIs defined in other specifications</h3><p>The <dfn id=dom-opendatabase title=dom-opendatabase><code>openDatabase()</code></dfn> method
1.91 ihickson 1785: must act as defined for the API with the same name on the
1.81 ihickson 1786: <code>Window</code> object in the HTML5 specification, with the
1787: exception that where the API would use the <span>origin</span> of
1788: the <span>active document</span> of the <span>browsing
1789: context</span> of the <code>Window</code> object on which the method
1790: was supposedly invoked, it must instead use the <span>origin</span>
1.92 ihickson 1791: of the script that invoked the method. <a href=#refsHTML5>[HTML5]</a><h3 id=interface-objects-and-constructors><span class=secno>5.4 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.81 ihickson 1792: the global scope of scripts whose <span>script execution
1793: context</span> is a <code><a href=#workerglobalscope>WorkerGlobalScope</a></code> object except for
1794: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1795: constructors defined by the XMLHttpRequest specifications, except
1796: that the <span>document response entity body</span> must always be
1797: null. <a href=#refsXHR>[XHR]</a></li>
1798:
1799: <li><p>The <code>WebSocket</code> interface object and
1800: constructor.</li>
1801:
1802: <li><p>The <code>MessageChannel</code> interface object and
1803: constructor.</li>
1804:
1805: <li><p>The <code title=dom-Worker><a href=#dom-worker>Worker()</a></code> and <code title=dom-SharedWorker><a href=#dom-sharedworker>SharedWorker(<var title="">url</var>)</a></code> constructors.</li>
1806:
1.82 ihickson 1807: </ul><h3 id=worker-locations><span class=secno>5.5 </span>Worker locations</h3><pre class=idl>interface <dfn id=workerlocation>WorkerLocation</dfn> {
1.81 ihickson 1808: readonly attribute DOMString <a href=#dom-workerlocation-href title=dom-WorkerLocation-href>href</a>;
1809: readonly attribute DOMString <a href=#dom-workerlocation-protocol title=dom-WorkerLocation-protocol>protocol</a>;
1810: readonly attribute DOMString <a href=#dom-workerlocation-host title=dom-WorkerLocation-host>host</a>;
1811: readonly attribute DOMString <a href=#dom-workerlocation-hostname title=dom-WorkerLocation-hostname>hostname</a>;
1812: readonly attribute DOMString <a href=#dom-workerlocation-port title=dom-WorkerLocation-port>port</a>;
1813: readonly attribute DOMString <a href=#dom-workerlocation-pathname title=dom-WorkerLocation-pathname>pathname</a>;
1814: readonly attribute DOMString <a href=#dom-workerlocation-search title=dom-WorkerLocation-search>search</a>;
1815: readonly attribute DOMString <a href=#dom-workerlocation-hash title=dom-WorkerLocation-hash>hash</a>;
1816: };</pre><p>A <code><a href=#workerlocation>WorkerLocation</a></code> object represents an <span>absolute
1817: URL</span> set at its creation.<p>The <dfn id=dom-workerlocation-href title=dom-WorkerLocation-href><code>href</code></dfn>
1818: attribute must return the <span>absolute URL</span> that the object
1819: represents.<p>The <code><a href=#workerlocation>WorkerLocation</a></code> interface also has the complement
1820: of <span>URL decomposition attributes</span>, <dfn id=dom-workerlocation-protocol title=dom-WorkerLocation-protocol><code>protocol</code></dfn>,
1821: <dfn id=dom-workerlocation-host title=dom-WorkerLocation-host><code>host</code></dfn>, <dfn id=dom-workerlocation-port title=dom-WorkerLocation-port><code>port</code></dfn>, <dfn id=dom-workerlocation-hostname title=dom-WorkerLocation-hostname><code>hostname</code></dfn>,
1822: <dfn id=dom-workerlocation-pathname title=dom-WorkerLocation-pathname><code>pathname</code></dfn>,
1823: <dfn id=dom-workerlocation-search title=dom-WorkerLocation-search><code>search</code></dfn>,
1824: and <dfn id=dom-workerlocation-hash title=dom-WorkerLocation-hash><code>hash</code></dfn>. These must
1825: follow the rules given for URL decomposition attributes, with the
1826: <span title=concept-uda-input>input</span> being the
1827: <span>absolute URL</span> that the object represents (same as the
1828: <code title=dom-WorkerLocation-href><a href=#dom-workerlocation-href>href</a></code> attribute), and
1829: the <span title=concept-uda-setter>common setter action</span>
1830: being a no-op, since the attributes are defined to be readonly. <a href=#refsHTML5>[HTML5]</a><h2 class=no-num id=references>References</h2><p class=big-issue>This section will be written in a future
1831: draft.<!--XXX--><h2 class=no-num id=acknowledgements>Acknowledgements</h2><!-- ACKS --><p>Thanks to
1832:
1833: Aaron Boodman,
1834: Алексей Проскуряков (Alexey Proskuryakov),
1835: Anne van Kesteren,
1836: Ben Turner,
1837: Dmitry Titov,
1838: Jonas Sicking,
1839: Justin James,
1840: Kevin Hakanson,
1841: Maciej Stachowiak,
1842: Michael Nordman,
1843: Mike Smith,
1844:
1845: and
1846:
1847: Philip Taylor
1848:
1849: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1850: technology and whose experience has been a huge influence on this
1851: specification.
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